Many different designs have been proposed in the past for providing a shaving instrument which provides a close, comfortable and safe shave. "Safety razors" are now common wherein a guard bar is disposed forwardly of the cutting edge of a leading blade while a skin-engaging cap member follows a trailing blade of a multi-blade shaving system. The guardbar and cap member help to control the angle at which the skin being shaved meets the cutting edges of the blades.
Since the 1970's razor systems have been marketed containing more than one shaving edge and a number of patents have issued covering such systems with two or more blades contained in the shaving unit. Overall, such multi-bladed shaving systems have been designed with blades that are made to deliver superior closeness, superior safety or some other desirable feature to the consumer. These systems contain blades which are formed from diverse materials and have a variety of coatings applied to them. In addition, the shape and geometry of the blades is generally different for each system.
The base material of the blade is one area in which blades are known to differ. U.S. Pat. No. 5,028,374, issued to Trotta discloses a blade for a safety razor which is manufactured from a block of uncured ceramic material. A portion is cut from the block, and a cutting edge is created by grinding and polishing an edge. U.S. Pat. No. 5,048,191, issued to Hahn and U.S. Pat. No. 5,056,227, issued to Kramer both also disclose blades made from ceramic material. U.S. Pat. No. 3,831,466, issued to Hicks discloses a blade which a blade is constructed from a plurality of vitreous materials.
The coating of blades is another area in which blades differ. U.S. Pat. No. 5,101,565, issued to Trankiem discloses razor blades which are coated with the residue of a heated mixture of a fluorocarbon polymer and a silane. Techniques for including interlayers between the substrate and the coating are also known. U.S. Pat. No. 5,142,785, issued to Grewal discloses a razor blade having an interlayer of molybdenum on the substrate and a outer coating of diamond or diamond-like material on the interlayer. U.S. Pat. No. 5,295,305, issued to Hahn further discloses an interlayer with a diamond or diamond-like coating on the interlayer.
Blade shape is one further factor which varies among systems. U.S. Pat. No. 5,153,992, issued to Brown discloses a blade for a safety razor having a plurality of sharp-edged apertures and a sharpened rectilinear edge for trimming. Further variables in the blade shape, such as circular, angular or polygonal cutting edges have also been disclosed, as have variations in the blade edge geometry caused by double facet or triple facet grinding. All of the above varieties deliver different properties to the blades and hence the quality of the shave experienced by the user can be varied through their use.
Another concept previously disclosed is to wrap all blades of a shaving system with a wire or thread to form a fencing element. This type of shaving system is particularly useful in maximizing safety and for use by people with sensitive skin. U.S. Pat. No. 1,035,548, issued Aug. 13, 1912, discloses a straight razor having a long blade on which is spirally wound a wire or thread to form a fencing element. Another form of fencing element is disclosed by Ferrara in U.S. Pat. No. 3,263,330, issued Aug. 2, 1966, wherein the razor blade cutting edge is encapsulated in a folded sheet of metal having a row of holes through which hair, but not skin, passes for cutting.
U.S. Pat. No. 3,505,734 issued to Iten on Apr. 14, 1970, discloses a cutting blade with a self-contained fencing element in the form of a wire. The wire or thread of selected diameter is wound about the body of the blade encompassing its ultimate edge. The spacing or pitch between successive turns of the wire is controlled relative to its diameter to provide protection to the skin of the user and to diminish the probability of cutting or nicking. The selected critical thread diameter and spacing between successive thread portions at the cutting edge of the blade allows the fenced portions of the blade to be drawn across the skin without coming into contact therewith. Some positional stability is given to the wound wire fencing elements by spot-welding them to the blade at a location back from its edge and by passing the wire through notches in the blade edge.
Another arrangement similar to that of Iten is disclosed in U.S. Pat. No. 3,750,285 to Michelson, issued on Aug. 7, 1973. The disclosed razor blade has a fenced cutting edge comprising a multiplicity of relatively short and thin fencing elements bent into relatively V-shaped form and secured to the blade edge by permanent attachment of the respective ends of each fencing element to the razor blade base structure at points relatively close to the blade cutting edge. Those fencing elements as well may be seated in notches formed in the blade edge or, if relatively softer than the blade edge, may have the blade edge embedded therein.
While the aforementioned designs of Iten and Michelson may be successful in insulating the skin from the ultimate cutting edge of the razor blade, they introduce difficulties into the manufacturing of razor blades incorporating their principal features. Initially, the thread or threads must be of flexible material having precise dimensional conformity. Secondly, it must also be sufficiently flexible for winding about the body of the blade or at least over the blade edge and yet strong enough to withstand severing as it passes over and comes into contact with the blade edge. It must be kept in mind that as the wire comes into contact with the ultimate edge of the blade, the edge being 300 to 500 Angstroms in radius, it necessarily damages the blade edge making such contact portion substantially incapable of providing comfortable shaving characteristics.
Techniques have been disclosed in U.S. patent application No. 645,055 filed Dec. 29, 1975, by Beddall for Printed Blade Shield, and U.S. Pat. No. 4,252,837 to Auton for Blade Shields, all being assigned to the same assignee as the present invention, for placing fencing elements on a blade edge without many of the shortcomings of the aforementioned prior art techniques. Specifically, epoxy resins may be placed on the edge and flanking facets of a blade using ink jet printing techniques or, alternatively, the fencing elements may be deposited by sputtering or ion plating. These techniques overcome some of the objections of the aforementioned prior art techniques. However, the fencing elements so deposited may be subject to dislodgement from the blade in response to normal shaving forces and/or abuse.
U.S. Pat. No. 4,211,006 to Halaby, et al, which issued on Jul. 8, 1980 and which is assigned to the same assignee as the present invention, discloses a razor blade having fencing elements deposited in recessed seats formed in the cutting edge and flanking surfaces of the blade by electroplating.
While the above-referenced publications disclose methods of making blades which will yield shaves with various characteristics, the designs do not allow for a mixing of the various blade characteristics to maximize closeness and comfort. It would therefore be desirable to provide a razor head which is not only comfortable but also provides a close shave. To this end, it would be desirable to provide a razor head which is comfortable and which provides a closer shave than multiple blade razor heads in which the multiple blades are identical to each other.